In article loading machines such as the bottle loading machine shown in applicant's U.S. Pat. No. 3,788,034 it is necessary to convey an empty case onto an elevator platform which raises the empty case immediately beneath a grid set having downwardly extending rigid fingers for directing the bottles into the empty case. Thereafter, the case is lowered and conveyed away from the elevator platform. Another empty case is then conveyed onto the elevator platform and the cycle is repeated. Such a cyclic operation is used on many conventional bottle loading machines which must employ some type of control apparatus to control the conveyancing and sequencing of the empty cases onto the elevator platform, raising and lowering of the platform, and removal of the case after loading.
The key to the successful operation of such an article loading machine is in the correct positioning of the empty case on the elevator platform so that the rigid fingers and the compartments in the empty case are perfectly aligned so as to enable the bottles to fall through the grid set into the case properly. If the case is positioned improperly on the platform, the case and grid set will be out of alignment causing bottles to be mis-loaded in the case further causing the loading machine to malfunction or possibly causing the bottles to fall out of the case onto the elevator platform or floor. A machine attendant must therefore be provided to correct the improper positioning of the case on the platform and any resulting malfunction of the bottle loading machine. Thus, the necessity of accurately positioning the empty case on the elevator platform can be seen to ensure continuing cyclic operation of the article loading machine.
One problem with the control devices of the prior art is that when the in-feed conveyor which transports the empty cases onto the platform is stopped, the inertia of the case causes it to drift on the platform and its position on the elevator platform cannot be accurately predetermined. An attempted solution to this problem has been to move the side rail members alongside the platform closer together so as to provide friction against the empty case thereby reducing its tendency to drift. However, such a solution is not very practical due to the use of many sizes of cases and the continual adjusting of the spacing between the side rail members.
Other prior article loading machines have used a continuously moving feed conveyor which comprises a flight bar extending across the conveyor which pushes the empty case onto the elevator platform and then continues downwardly past the platform to trip a switch to effect raising of the elevator platform. However, the problem with such a system is that the article loading machine has no way of knowing whether or not an empty case is sitting on the elevator platform. If for some reason an empty space existed on the conveyor and a case was not conveyed onto the elevator platform by the flight bar, the flight bar would still proceed downwardly to the switch causing the elevator platform to be raised beneath the grid set resulting in the glass bottles being dropped onto an empty elevator. Such an event happens quickly and if the machine operator is not watching at the moment the empty bottles can be broken over the floor causing a costly delay and interruption in the operation of the machine. Hence, such a system will operate whether or not a case is on the elevator platform during the operational cycle.